Incorporating arrays of josephson junctions in a josephson junction ring modulator in a josephson parametric converter

ABSTRACT

A Josephson parametric converter is provided. The Josephson parametric converter includes a multi-Josephson junction ring modulator having a first, a second, a third, and a fourth node and a first, a second, a third, and a fourth array of N Josephson junctions arranged in a ring configuration with the nodes inter-dispersed between the arrays. The first array is between the first and second nodes, the second array is between the second and third nodes, the third array is between the third and fourth nodes, and the fourth array is between the fourth and first nodes. N is an integer having a value greater than one. The Josephson parametric converter further includes a first and a second resonator formed from lumped-element capacitors that shunt the multi-Josephson junction ring modulator and respectively enable a first and a second mode of the Josephson parametric converter.

BACKGROUND

Technical Field

The present invention relates generally to electronic devices and, inparticular, to incorporating arrays of Josephson junctions in theJosephson ring modulators which constitute the nonlinear dispersivemedium in Josephson parametric converters.

Description of the Related Art

A Josephson ring modulator (JRM) is a nonlinear dispersive element basedon Josephson tunnel junctions that can perform three-wave mixing ofmicrowave signals at the quantum limit. The JRM consists of JosephsonJunctions (JJs). In order to construct a non-degenerate parametricdevice that is the Josephson parametric converter (JPC), which iscapable of amplifying and/or mixing microwave signals at the quantumlimit, the JRM is incorporated into two microwave resonators at anRF-current anti-node of their fundamental Eigenmodes. As has beendemonstrated in several experimental and theoretical works, theperformances of these JPCs, namely power gain, dynamical bandwidth, anddynamic range, are strongly dependent on the critical current of the JJsof the JRM, the specific realization of the electromagnetic environment(i.e., the microwave resonators), and the coupling between the JRM andthe resonators.

SUMMARY

According to an aspect of the present principles, a Josephson parametricconverter is provided. The Josephson parametric converter includes amulti-Josephson junction ring modulator having a first, a second, athird, and a fourth node and a first, a second, a third, and a fourtharray of N Josephson junctions arranged in a ring configuration with thenodes inter-dispersed between the arrays. The first array is between thefirst and second nodes, the second array is between the second and thirdnodes, the third array is between the third and fourth nodes, and thefourth array is between the fourth and first nodes. N is an integerhaving a value greater than one. The Josephson parametric converterfurther includes a first and a second resonator formed fromlumped-element capacitors that shunt the multi-Josephson junction ringmodulator and respectively enable a first and a second mode of theJosephson parametric converter.

According to another aspect of the present principles, a method isprovided. The method includes forming a Josephson parametric converter.The forming step includes forming a multi-Josephson junction ringmodulator having a first, a second, a third, and a fourth node and afirst, a second, a third, and a fourth array of N Josephson junctionsarranged in a ring configuration with the nodes inter-dispersed betweenthe arrays. The first array is between the first and second nodes, thesecond array is between the second and third nodes, the third array isbetween the third and fourth nodes, and the fourth array is between thefourth and first nodes. N is an integer having a value greater than one.The forming step further includes forming a first and a second resonatorfrom lumped-element capacitors that shunt the multi-Josephson junctionring modulator and respectively enable a first and a second mode of theJosephson parametric converter.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows an exemplary circuit for a Josephson Parametric Converter(JPC) 100, in accordance with an embodiment of the present principles;

FIG. 2 an exemplary implementation layout for the Josephson ParametricConverter (JPC) 100 of FIG. 1, in accordance with an embodiment of thepresent principles; and

FIG. 3 shows an exemplary method 300 for forming a Josephson ParametricConverter (JPC) 100, in accordance with an embodiment of the presentprinciples.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present principles are directed to incorporating arrays of JosephsonJunctions in Josephson Ring Modulators (JRMs) which form the nonlineardispersive medium in Josephson Parametric Converters (JPCs).

In an embodiment, we replace four Josephson Junctions (JJs), which forma conventional standard JRM, with an array of large junctions (havinglarge critical current) in each arm (larger than 1, e.g., between 2 and15). In an embodiment, we also modify the electromagnetic environment insupport of the new JRM. In an embodiment, we propose usinglumped-element capacitances which form, in conjunction with theinductance of the JRM, the necessary microwave resonators of the JPC.

By introducing the changes described herein to JPCs, we aim at enhancingtwo main performances of JPCs, namely the dynamical bandwidth and thedynamic range of the JPCs. Conventional JPC devices suffer from arelatively low dynamical bandwidth on the order of 10 MHz and a maximuminput power of a few photons at the signal frequency per dynamicalbandwidth at 20 dB of gain. Enhancing these two figures of merit by atleast an order of magnitude is critical so that JPCs can be applicablefor scalable qubit readout architectures. In an embodiment, we canprovide a larger dynamic range (x10-100) due to stiffer pump and also byemploying arrays of JJs in the Josephson Junction Ring Modulators(JRMs). In an embodiment, we can provide a larger dynamicalbandwidth >100 MHz (by increasing the participation ratio of the ring).Another important advantage of the proposed new device with regard toscalability is its small footprint. Compared with microstrip JPCs forinstance the size of the new device is expected to be about 300 timessmaller.

To understand how this new configuration can enhance the dynamicalbandwidth of JPCs, it is important to note that one of the limitationson the amplifier bandwidth is what is known as the pQ product, where Qis the total quality factor of the resonators and p is the participationratio of the device (i.e., the ratio between the effective inductance ofthe ring to the total inductance of the device). In order for the JPC towork properly, the pQ product of the device should be much larger thanunity. In microstrip resonators, the participation ratio is relativelylow on the order of a few percent, therefore in order to satisfy the pQproduct limitation, the Q of the resonators should be relatively “large”on the order of 100. Hence, in order to enhance the bandwidth of thedevice, we suggest dominating the total inductance of the device via thering contribution while maintaining a large critical current at the sametime, which should allow us to lower Q by a factor of 10 or more andconsequently obtain a dynamical bandwidth on the order of 100 MHz at 20dB of gain.

As to the dynamic range figure, the proposed device is expected to haveenhanced performance for two reasons. One, the fact that the resonatorsin this new configuration would be made out of lumped-elements, whichlack any resonance close in frequency to the pump tone driving thedevice, makes the pump drive stiffer than existing designs (especiallymicro strip JPCs) and therefore boosts the dynamic range of the device.Two, substituting the single large JJ in each arm of the JRM with anarray of large JJs (having the same critical current as the single JJ)would increase the maximum RF-voltage difference that can be appliedacross the array compared to the single junction case. As a consequence,the maximum circulating power that can be handled by the proposedMulti-JJ ring modulator (MJRM) is expected to be larger. In other words,the addition of arrays of JJs is expected to decrease the nonlinearityof the JRM by decreasing the coupling constant of the three-wave mixingmedium (i.e. the JRM), and as a result require driving it with higherpump powers in order to achieve the same gains. In summary, theincorporation of arrays of large Josephson junctions in the Josephsonjunction ring modulator in conjunction with using lumped-elementimplementations for the resonators, should enhance the maximum inputpower (i.e., dynamic range) of Josephson parametric converters to morethan −120 dBm at 20 dB of gain.

FIG. 1 shows an exemplary circuit for a Josephson Parametric Converter(JPC) 100, in accordance with an embodiment of the present principles.

The JPC 100 includes a Multi-JJ ring modulator (MJRM) 110. The MJRM 110includes four nodes 101, 102, 103, and 104. The MJRM 110 furtherincludes four arrays of N Josephson junctions 111A, 111B, 111C, and 111Darranged in a Wheatstone Bridge-like configuration with respect to thefour nodes 101-104 (that is, in a ring configuration with the nodes101-104 inter-dispersed between the arrays 111A-111D), where array 111Ais between nodes 101 and 102, array 111B is between nodes 102 and 103,array 111C is between nodes 103 and 104, and array 111D is between nodes104 and 101. The N Josephson junctions in each of the arrays 111A-D areconnected in series, where N is an integer larger than one. The arrays111A-D form a superconducting loop threaded by a magnetic flux Φ_(ext).In an embodiment, the flux bias applied to the ring is half aflux-quantum.

The JPC 100 also includes 2 resonators denoted as a and b. Theresonators are formed by shunting opposite nodes of the MJRM 110 withlumped-element capacitors 141-144. Thus, nodes 101 and 103 are shuntedwith lumped-element capacitors C_(a) 141 and C_(a) 142, and nodes 102and 104 are shunted with lumped-element capacitors C_(b) 143 and C_(b)144. Capacitor C_(a) 141 and capacitor C_(a) 142 are connected in serieswith respect to each other, and capacitor C_(b) 143 and capacitor C_(b)144 are connected in series with respect to each other. Each resonatoris connected to two feedlines either directly or through couplingcapacitors. Resonator a is connected to two feedlines, which form thesignal (S) port, via lumped-element capacitors C_(c) ^(a) 131 and C_(c)^(a) 132. Each feedline is connected to one output port of the hybrid199. Resonator b is connected to two feedlines, which form the idler (I)port, via lumped-element capacitors C_(c) ^(b) 133 and C_(c) ^(b) 134.Each feedline is connected to one output port of the hybrid 199. Theresonance frequencies (differential Eigenmodes) of the JPC in thisconfiguration are mainly determined by the shunt capacitances 141-144(C_(a) 141, C_(a) 142, C_(b) 143, and C_(b) 144), the linear inductanceof the MJRM 110, the coupling capacitors 131-134 (C_(c) ^(a), 131, C_(c)^(a) 132, C_(c) ^(b) 133, and C_(c) ^(b) 134), and the characteristicimpedances of the feedlines. Without loss of generality, we refer tomicrowave tones that lie within the bandwidths of resonators a and b assignal (S) and (I) tones, respectively and, therefore, refer to thephysical port connected to resonator a as the signal port and thephysical port connected to resonator b as the idler port. We furtherassume, without loss of generality, that the resonance frequency ofresonator b is larger than the resonance frequency of resonator a.

In JPC 100, two 180 degree hybrid couplers 199 (also interchangeablyreferred to as “hybrids” in short) are used, one on the left side andone on the right side as shown. Each of the hybrids functions as a powerdivider with two input ports and two output ports. A microwave signalthat enters the difference port of the hybrid is split in half. Half ofthe signal power exits on one output port of the hybrid while the otherhalf exits on the other output port of the hybrid. However, the phasedifference between these two output signals is 180 degrees (hence, theterm “difference port”). A microwave signal that enters the sum port isalso split in half in the same manner, but the phase difference betweenthe output signals is zero (the phases are equal). In FIG. 1, the outputports of the hybrids are connected to the coupling capacitors 131, 132,133, and 134. Based on the preceding, microwave signals that are fedthrough the sum and difference ports of the hybrid are coupled to thedevice through both output ports of the hybrid.

The signal (S) and the idler (I) tones represent microwave signals thatlie within the dynamical bandwidths of resonators a and b of the JPC 100respectively. The signal (S) tone is fed through the difference port (Δ)of an 180° hybrid coupler 199. The idler (I) tone is fed through thedifference port (Δ) of another 180° hybrid coupler 199. A third tone,denoted as pump (P), is non-resonant and is input to the MJRM 110 viathe sum port (Σ) of one of the 180° hybrid couplers 199 connected toeither side of the device. The unused sum port (Σ) of the second hybrid199 is connected to a 50 Ohm termination. Both the signal (S) and theidler (I) excite the MJRM differentially, while the pump (P) is acommon-mode drive. Thus, the signal (S) and the idler (I) couple to thedifferential modes of the MJRM 110, while the pump (P) couples to thecommon-mode of the MJRM 110. The frequency of the signal (S) tone isf_(S), the frequency of the idler (I) tone is f_(I), and the frequencyof the pump drive is set to either the sum or the difference of f_(S)and f_(I).

The proposed MJRM also covers the variation in which it allows theresonance frequencies of resonators a and b to be tuned by varying theapplied flux threading the MJRM loop. One way to achieve that is byshunting each array of N JJs by linear inductance which satisfies thecondition N*L_(J)/4<L<N*L_(J)/2, where L is the linear inductance of theshunt, N is the number of JJs in the array, and L_(J) is the linearinductance of each JJ in the array at the working point (i.e., theapplied flux threading the MJRM). The linear shunt inductance L can beimplemented using narrow superconducting wires, or array of large JJs.

FIG. 2 an exemplary implementation layout for the Josephson ParametricConverter (JPC) 100 of FIG. 1, in accordance with an embodiment of thepresent principles.

The JPC 100 includes a dielectric substrate 210 on which the MJRM 110 isdisposed. Further on the dielectric substrate 210, a superconductorlayer (hereinafter “superconductor” in short) 221 is arranged toencompass the periphery of the MJRM 110. A cut or gap 210 is provided inthe superconductor 221 for proper operation of the JPC 100. In furtherdetail, the cut 210 is provided to prevent any loops in superconductorlayer 221. That is, superconductor layer 221 is not continuous and,hence, does not include a closed loop. Thus, no current is able tocirculate in layer 221.

On the superconductor 221, eight low-loss dielectrics 222 are providedas follows and as shown in FIG. 2. Four low-loss dielectrics 222 areprovided in the middle portion of JPC 100 around MJRM 110 to implementcapacitors C_(a) 141, C_(a) 142, C_(b) 143, and C_(b) 144. Four low-lossdielectrics 222 are provided on the sides to implement couplingcapacitors. It is to be appreciated that in other embodiments, thedielectric layer in the middle section (four low-loss dielectrics 222)can cover the whole periphery of the MJRM 110 on top of thesuperconductor 221 without affecting the performance of the JPC 100.Eventually, what defines the plate capacitors is the overlap between theupper and bottom electrodes. On at least portions of the eight low-lossdielectrics 222, superconductors 223 are disposed. Superconductors 223implement the top electrode of capacitors C_(a) 141, C_(a) 142, C_(b)143, C_(b) 144, C_(c) ^(a) 131, C_(c) ^(a) 132, C_(c) ^(b) 133, andC_(c) ^(b) 134. Superconductors 223 also connect one end of C_(c) ^(a)131 to one end of C_(a) 141, one end of C_(c) ^(a) 132 to one end ofC_(a) 142, one end of C_(c) ^(b) 133 to one end of C_(b) 143, and oneend of C_(c) ^(b) 134 to one end of C_(b) 144. The MJRM 110 is connectedto the superconductors 223. The superconductors 221 implement thesuperconducting feedlines (transmission lines) for the 3 Eigenmodes ofthe JPC 100. The device feedlines that connect to the output ports ofthe hybrids (which are shown in FIG. 1) are in superconductor layer 221.

FIG. 3 shows an exemplary method 300 for forming a Josephson ParametricConverter (JPC) 100, in accordance with an embodiment of the presentprinciples. It is to be appreciated that one or more steps have beenomitted from method 300 for the sake of brevity, but are readilyapparent to one of ordinary skill in the art given the teachings of thepresent principles provided herein.

At step 310, provide a dielectric substrate.

At step 320, form, on the dielectric substrate, a multi-Josephsonjunction ring modulator having a first, a second, a third, and a fourthnode and a first, a second, a third, and a fourth array of N Josephsonjunctions arranged in a ring configuration with the nodesinter-dispersed between the arrays. The first array is between the firstand second nodes, the second array is between the second and thirdnodes, the third array is between the third and fourth nodes, and thefourth array is between the fourth and first nodes. In an embodiment, Nis an integer having a value greater than one.

At step 330 provide a superconductor layer around the MJRM that includesa gap. In an embodiment, the superconductor layer is provided, forexample, using any layer deposition process, and then the gap is made,for example, using any known process including, but not limited toetching.

At step 340, form a first resonator and a second resonator by shuntingthe MJRM with lumped-element capacitors.

At step 350, connect the first resonator and the second resonator to twoports, where each of the two ports includes two respective feedlines.

A description will now be given regarding some exemplary applications towhich the present principles can be applied.

The present principles can be used in the readout of solid state qubitssuch as superconducting qubits and quantum dots. For example, thepresent principles can be used to enhance the measurement fidelity, andallow for scalable readout architectures. The present principles canalso be used, in general, to perform sensitive quantum measurements inthe microwave domain, such as measuring nanomechanical systems coupledto microwave resonators.

The present principles can be used in building wideband, large inputpower quantum-limited Josephson directional amplifiers and also on-chipdissipationless circulators. The present principles can be used (similarto Josephson parametric converters but with enhanced performance) asideal microwave mixers (performing upconversion and downconversion ofmicrowave frequency without dissipation), controllable microwavebeam-splitters, and fast, lossless microwave switches.

The present principles can also find some applications in improving thesensitivity of microwave measurements in the areas of astronomy andcosmology.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A Josephson parametric converter, comprising: amulti-Josephson junction ring modulator having a first, a second, athird, and a fourth node and a first, a second, a third, and a fourtharray of N Josephson junctions arranged in a ring configuration with thenodes inter-dispersed between the arrays, wherein the first array isbetween the first and second nodes, the second array is between thesecond and third nodes, the third array is between the third and fourthnodes, and the fourth array is between the fourth and first nodes, and Nis an integer having a value greater than one; and a first and a secondresonator formed from lumped-element capacitors that shunt themulti-Josephson junction ring modulator and respectively enable a firstand a second mode of the Josephson parametric converter.
 2. TheJosephson parametric converter of claim 1, wherein the N Josephsonjunctions in each of the arrays are connected in series.
 3. TheJosephson parametric converter of claim 1, wherein the first resonatorcomprises at least one capacitor shunted across the first node and thethird node, and the second resonator comprises at least one othercapacitor shunted across the second node and the fourth node.
 4. TheJosephson parametric converter of claim 3, wherein multi-Josephsonjunction ring modulator has two opposing pairs of nodes, a first of thetwo opposing pairs of nodes formed from the first node and the thirdnode, and a second of the two opposing pairs of nodes formed from thesecond node and the fourth node.
 5. The Josephson parametric converterof claim 1, further comprising a first, a second, a third, and a fourthcoupling capacitor, each having a first electrode connected to arespective different one of the nodes of the multi-Josephson junctionring modulator, and having a second electrode for connecting to arespective one of a plurality of feedlines.
 6. The Josephson parametricconverter of claim 1, wherein the Josephson parametric converter isformed such that a total inductance of the Josephson parametricconverter is dominated by an inductance contribution of themulti-Josephson junction ring modulator to provide a dynamical bandwidthof at least 100 MHz for the Josephson parametric converter at 20 dB ofgain.
 7. The Josephson parametric converter of claim 1, wherein thefirst and the second resonator are further formed from lumped-elementinductance, and wherein the arrays of Josephson junctions in theJosephson junction ring modulator in conjunction with using alumped-element implementation for the resonators enables a maximum inputpower of at least −120 dBm at 20 dB of gain for the Josephson parametricconverter, wherein the lumped-element implementation for the resonatorscomprises the lumped-element capacitors and the lumped-elementinductance.
 8. The Josephson parametric converter of claim 1, wherein Nis equal to an integer larger than one.
 9. The Josephson parametricconverter of claim 1, wherein the Josephson parametric converter isconfigured to perform wave mixing of three microwave signals for quantuminformation processing.
 10. The Josephson parametric converter of claim9, wherein the Josephson parametric converter is configured toselectively perform unitary frequency conversion or quantum-limitedamplification in a microwave domain based on a pump tone frequency. 11.A method, comprising: forming a Josephson parametric converter, whereinsaid forming step includes: forming a multi-Josephson junction ringmodulator having a first, a second, a third, and a fourth node and afirst, a second, a third, and a fourth array of N Josephson junctionsarranged in a ring configuration with the nodes inter-dispersed betweenthe arrays, wherein the first array is between the first and secondnodes, the second array is between the second and third nodes, the thirdarray is between the third and fourth nodes, and the fourth array isbetween the fourth and first nodes, and N is an integer having a valuegreater than one; and forming a first and a second resonator fromlumped-element capacitors that shunt the multi-Josephson junction ringmodulator and respectively enable a first and a second mode of theJosephson parametric converter.
 12. The method of claim 11, wherein theN Josephson junctions in each of the arrays are connected in series. 13.The method of claim 11, wherein forming the first and the secondresonator comprise: shunting at least one capacitor across the firstnode and the third node; and shunting at least one other capacitoracross the second node and the fourth node.
 14. The method of claim 13,wherein multi-Josephson junction ring modulator is formed to have twoopposing pairs of nodes, a first of the two opposing pairs of nodesformed from the first node and the third node, and a second of the twoopposing pairs of nodes formed from the second node and the fourth node.15. The method of claim 11, further comprising forming a first, asecond, a third, and a fourth coupling capacitor, each having a firstelectrode connected to a respective different one of the nodes of themulti-Josephson junction ring modulator, and having a second electrodefor connecting to a respective one of a plurality of feedlines.
 16. Themethod of claim 11, wherein the Josephson parametric converter is formedsuch that a total inductance of the Josephson parametric converter isdominated by an inductance contribution of the multi-Josephson junctionring modulator to provide a dynamical bandwidth of at least 100 MHz forthe Josephson parametric converter.
 17. The method of claim 11 whereinthe first and the second resonator are further formed fromlumped-element inductance, and wherein the arrays of Josephson junctionsin the Josephson junction ring modulator in conjunction with using alumped-element implementation for the resonators enables a maximum inputpower of at least −120 dBm at 20 dB of gain for the Josephson parametricconverter, wherein the lumped-element implementation for the resonatorscomprises the lumped-element capacitors and the lumped-elementinductance.
 18. The method of claim 11, wherein N is equal to an integerlarger than one.
 19. The method of claim 11, wherein the Josephsonparametric converter is configured to perform wave mixing of three inputwaves for quantum information processing.
 20. The method of claim 19,wherein the Josephson parametric converter is configured to selectivelyperform unitary frequency conversion or quantum-limited amplification ina microwave domain based on a pump tone frequency.